Technical Field
The present invention relates to a damper disc assembly, particularly to a damper disc assembly configured to attenuate variation in torque inputted thereto from an engine and transmit the torque toward a transmission.
Background Art
In general, noises and vibrations of vehicles include noises in idling, noises in traveling and tip-in/tip-out (low frequency vibrations). Damper disc assemblies are provided for inhibiting the aforementioned noises and vibrations.
In torsional characteristics of a damper disc assembly, a low torsion angular range relates to noises in idling, and a low torsional stiffness is preferable in the low torsion angular range. On the other hand, to countermeasure tip-in/tip-out, the torsional characteristics are required to have a highest possible stiffness.
To solve the aforementioned problems, there has been produced a type of damper disc assembly using two kinds of springs so as to implement two-stage torsional characteristics. This device is configured to suppress low both torsional stiffness and hysteresis torque in the first stage (low torsion angular range) of the torsional characteristics so as to inhibit noises in idling. Additionally, this device is configured to set both torsional stiffness and hysteresis torque to be high in the second stage (high torsion angular range) of the torsional characteristics so as to attenuate vibrations of tip-in/tip-out.
Moreover, there has been also produced a type of device that when minute vibrations attributed to, for instance, variation in engine combustion are inputted in the high torsion angular range of the torsional characteristics, a low hysteresis torque is configured to be generated without generating a high hysteresis torque so as to attenuate the minute vibrations (see e.g., Japan Laid-open Patent Application Publication NO. H11-280784).
Furthermore, there has been also proposed a construction of a damper disc assembly obtained by dividing a spline hub in a well-known damper disc assembly into a hub and a flange so as to particularly widen the first stage low torsion angular range as much as possible (see e.g., Japan Laid-open Patent Application Publication No. H10-339355). In this construction, the divided hub and flange are coupled by a sub damper unit in a rotational direction. Additionally, the sub damper unit is disposed laterally to the flange.